Meta-data is “data about data,” and is used as data which explains binary data such as video data or audio data. However, when binary data and meta-data corresponding thereto exist in separate files, when moving or copying files, the user must simultaneously manage the binary data and the meta-data, which is very troublesome.
For this reason, in order to simplify management of binary data and meta-data, various methods of writing binary data and meta-data have conventionally been proposed. This type of conventional art can be divided into methods which stipulate a new binary format, and methods of managing in a database.
First, examples of methods which stipulate a new binary format include, for image data, Tiff, Exif, and Flashpix. FIG. 16 schematically shows a format which incorporates meta-data into binary data. Binary data is, for example, image data. A typical method of incorporating meta-data into binary data, as shown in FIG. 16, is to provide in the header portion of the image data a domain for writing meta-data, into which the user writes the meta-data. Writing meta-data in this way facilitates data searching and classification. Further, since the meta-data is included in the binary data, both can be managed as a single file, making file management comparatively easier.
Next, a method of managing binary data and meta-data in a database will be explained. FIG. 17 schematically shows a method of managing binary data and meta-data in a database. Methods like that shown in FIG. 17, which use a database, etc. to manage binary data and meta-data existing as separate files, are widely used. These methods have the advantage that existing binary data can be used as is in existing applications.
It is also commonly known that a directory structure can be used in file management. Accordingly, when, for example, managing a large number of binary data files, all of the binary data files are usually not placed in a single directory, but a plurality of sub-directories are created, one for each group of binary data files sharing a certain affiliation or characteristic. In this case, the meta-data for all of the binary data files in a given sub-directory have an item in common. However, at present, each binary data file exists separately, and meta-data is managed by one of the two methods discussed above.
Both methods which stipulate a new format for writing meta-data and methods which manage meta-data using a database have their respective problems.
First, when a new format for writing meta-data is stipulated, existing binary data must be converted into that new format, and then the meta-data written into the new format. Further, in order to use the meta-data in the new format for searching, applications compatible with the new format are necessary. In other words, the drawback of this method is that writing and using the meta-data require a very large number of steps and a special environment. In addition, in order to process binary data in the new format (in the case of image data, to replay the image, for example), applications compatible with the new data format are necessary, and existing applications cannot be used.
Moreover, since the method of writing the meta-data is uniquely determined by the new format, a further problem is that in order to prepare an application which uses meta-data in the new format, it is necessary to create new routines for searching the meta-data. In addition, the prescribed format must be changed in order to write meta-data in a new domain.
On the other hand, when using a database to simultaneously manage binary data and meta-data, meta-data cannot be recorded or used without database software. Further, special software is also necessary to display recorded meta-data. In addition, when binary data is taken out of the database, it is not accompanied by the corresponding meta-data, and becomes binary data without meta-data.
When using a directory structure to manage binary data files, as well, the meta-data for binary data files in a given directory exist for each binary data file, and are managed as separate files. Consequently, even when a plurality of binary data files share an item in common, each binary data file is managed independently, thus increasing the data quantity of meta-data which must be managed. Further, when changing an item in common, meta-data for each binary data file changed must also be changed.